Wondering if anyone else has experienced this, but I had my controller connected to the USB cable to charge, but decided it was uncomfortable to play with so I tried disconnecting it while in the map voting screen. The dialog popped up telling me to plug my controller in, and it booted me from the game. Not only that, but it kept the map voting screen up, and I was unable to go back to the matchmaking menu. I had to reset the game entirely in order to continue. I haven’t tried replicating results with a controller dying due to low batteries, but I am sure a similar issue occurs. Unsure whether or not this might happen at other stages in matchmaking either, but my guess is that the battery warning popup took precedence and cancelled everything when it should not do so.
Let me know if you have this issue as well.